1. Field of the Invention
The present invention relates to a drawer mechanism that allows units to be pulled out from a certain apparatus main body and to an image forming apparatus equipped with the same.
2. Description of the Related Art
An image forming apparatus, such as a copying machine, is often configured in such a manner that respective units can be pulled out in order to facilitate maintenance. Units that can be pulled out include a paper feeding cassette, a primary paper feeding unit, an intermediate feed unit, a developing unit, a drum unit, a toner container, and a discharge unit. During paper jam processing or at the occurrence of empty toner or empty paper, the user is able to carry out the task by pulling out the corresponding unit. Various types have been proposed regarding the mechanism that allows units to be pulled out, of which a typical mechanism adopting a rail will now be described by way of example.
According to the slide rail disclosed in JP-A-2001-173305 (D1), an outer rail is fixed to the interior of the housing of a copying machine while an inner rail is attached in such a manner that it can be pulled out and pushed in by sliding it along the outer rail. The end edges of the inner rail are received in a space between rollers attached to an overhanging portion of the outer rail. A roller attached to a tapered portion of the inner rail fits in a space between the end edges of the outer rail. The both rails are thus combined without wobbling and the inner rail is rendered slidable.
JP-A-9-240849 (D2) discloses an image forming apparatus having a paper feeding tray that can be pulled out, a guide rail for the paper feeding tray, and a rotatable guide roller provided to the guide rail on the front side. In this apparatus, a hole in which the guide roller falls when the paper feeding tray is set in the apparatus main body at the predetermined position is made in the guide surface of the paper feeding tray.
JP-A-6-149015 (D3) discloses a corona discharger formed of a coroner discharger main body opposing the photosensitive body and a guide rail that supports the discharger main body in an attachable and detachable manner. The guide rail is a member having a U-shaped cross section, and it has plural pairs of guide protrusions on the mutually opposing inner walls. The corona charger main body is formed of a casing having an almost U-shaped cross section and a corona wire stretched across the interior of the casing. The corona discharger main body can be attached by inserting guided portions that protrude sideways from the both side walls of the casing into attachment spaces defined between the guide protrusions inside the guide rail. In addition, a distance from the corona discharger to the photosensitive body can be changed by choosing the attachment spaces.
According to the apparatus of D1, it is configured in such a manner that the outer rail is fixed to the copying machine main body and the inner rail is allowed to slide along the outer rail. This configuration requires both the outer rail and the inner rail. Hence, the number of components is large and the cost and the weight are increased.
According to the apparatus of D2, it is configured in such a manner that the guide rail is fixed to the copying machine main body and the sliding plate provided to the paper feeding tray is allowed to slide along the guide rail. This configuration requires both the guide rail and the sliding plate. Hence, as with the apparatus of D1, the number of components is large and the cost and the weight are increased.
According to the apparatus of D3, the drawer mechanism is formed by engagement of the guide rail and the casing without using any roller, and larger resistance is generated when a unit is pulled out. Hence, this configuration is not preferable for a drawer mechanism adopted in an image forming apparatus because the respective units therein are heavy components and resistance load becomes larger.